Gene expression in diseased and healthy cells and in cells in different stages of development is oftentimes different and characterizable. The ability to monitor gene expression in such cases provides researchers and medical professionals with a powerful diagnostic tool.
One can monitor gene expression, for example, by measuring the presence or absence of a nucleic acid (e.g., a mRNA) that is the transcription product of a gene of interest. Monitoring the nucleic acid may be accomplished by chemically or biochemically labeling the mRNA with a detectable moiety followed by hybridization to a nucleic acid probe for the gene. The detection of a labeled nucleic acid at the probe position indicates that the targeted gene has been expressed.
Various methods of RNA detection have been developed. These include the “Northern” blotting procedure and the use of radioactive isotobes such as 32P. Non-radioactive detection techniques have also been developed. Langer et al., Proc. Natl. Acad. Sci. USA 1981, 78, 6633-6637, for example, disclosed certain biotin labeled nucleosides. Lockhart et al., U.S. Pat. No. 6,344,316, disclosed enzymatic methods of end-labeling a with non-radioactive nucleotides. These references are each incorporated herein for all purposes by reference.
There remains, however, a need for RNA labeling compounds which can be used for efficient and accurate labeling of RNA and monitoring of gene expression.